Original Research Article

Sunsari Technical College Journal 2015; 2(1):38-43 ISSN: 2091-2102 (online) :2467-9224(print)

OPTIMIZATION OF PROCESSING PARAMETERS AND EXTENSION OF SHELF LIFE OF ‘QUARK’-A TYPE OF THICK YOGHURT

Ram Shovit Yadav1* 1Sunsari Technical College, Department of Food Technology, Dharan, Nepal *Corresponding author email: [email protected]

Received: 5.6.2015; Revised and Accepted- 25.8. 2015

DOI:http://dx.doi.org/10.3126/stcj.v2i1.14797

Abstract Quark was prepared from cow milk by the optimization of different parameters like concentration of rennet, sugar percentage and flavor types. The rennet concentration used for optimization was 0.00139 %, 0.00234 %, 0.00278 % and 0.00468 %. In terms of acidity, texture, flavor and appearance. 0.00234 percent rennet was found significantly best product. The concentration of sugar in quark was varied in different proportion viz. 2, 4 and 5 %, among these 4 % was ranked best with respect to sensory properties. Flavor optimization with vanilla 125ppm without color addition was preferred significantly. Though the high quality life (HQL) of the optimized product was 45 days in deep frozen condition (-20oC), 6 days in refrigerated condition (-4oC). Yet, the product remained acceptable up to 2 days at room temperature (33 ± 2oC) and up to 15 days in refrigerated condition. Key words:- Quark, Rennet, Coagulation, whey

INTRODUCTION added in the form of mesophilic lactococcus starter culture. Quark is acid dairy product originating from Germany, Continuing acidification until the pH reaches 4.6, which causes resembles with yoghurt of thick consistency. It was introduced precipitation of the casein proteins. In Germany, the curd is (in Holland) as a fat free dairy product and is exactly a very continuously stirred to prevent it from getting hard, resulting in fresh kind of cheese. Quark is made by adding rennet or another a thick, creamy texture. souring agent (like Buttermilk) to milk. The milk then separates To make the firmer eastern European version, a small amount of into whey and curds. The whey is poured off or drained. The rennet may be added to make the curd firmer. Some or most of remaining curds are stirred until a smooth consistency is the whey is removed to standardize the quark to the desired reached: this is called quark. Dictionaries usually translate it as thickness1. curd cheese. It is soft, white and un-aged, similar to Fromage frais, but with a higher fat content1. Quark is cultured dairy Amount of lactic acid production by L.bulgaricus is 1.7-1.8% products obtained by fermenting milk to pH of 4.3 to 4.8 with while S.thermophilus is 0.6-0.8%. Acid contributes to the mixed mild cheese cultures, usually comprising Streptococus formation of gel by conversion of colloidal calcium-phosphate cremoris and Streptococus lactis and sometimes Streptococcus complex present in the casein micelle to soluble calcium diacetylactis. This is followed by removal of whey and phosphate fraction. At pH 4.6-4.7 this leads to loss of calcium concentration of solids to obtain a stiff, white to off white, from micelles and coagulation of casein.2 spreadable paste that should be homogenous, short textured and Rennet consists of mainly rennin and pepsin, principally the free from serum of graininess. The product should have clean former being responsible for milk clotting and the latter for lactic flavor and be mildly acidic. Rennet is usually added proteolysis (although both possess the two characteristics). during fermentation to assist in curd formation and improve the Rennin is liable to heat and alkali besides other physical and separation of whey1. chemical agents and gets inactivated at pH 6.8 - 7.0 at70oC in 14 Quark is a member of the acid set cheese group, meaning it is minute3. traditionally made without the aid of rennet. Because quark is MATERIALS AND METHODS consumed without aging, in the United States the milk must first be pasteurized. Once the milk is ready, lactic acid bacteria are Raw materials and sources

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About 15 liters of fresh whole cow milk was taken for each lot Collect the drain whey to calculate the Quark yield 75% whey of quark preparation. The temperature and acidity of the milk at +curd) the time of collection was 16oC and 0.14 % respectively. The milk was collected within the two hours of milking and the pH of the milk was 6.4 Adding of sugar Rennet powder Information from the label: Homogenizing STAMINS 1150, NATUREN™ Packaging CHR. HANSEN, DENMARK Instruction: to use approx. 3g/100lt milk Ready for consumption Store at -15oC Fig 3.1 Process employed for making Quark.

Preparation of rennet solution Recipe formulations 1. First optimization of rennet Rennet 0.1 gm was mixed in 50 ml distilled water at normal A = 500 ml milk + 1ml of 0.234 % rennet + 2 % temperature (25°C) and was agitated until completely starter culture solubilized. It was cooled in the freezer at 5°C. One ml of rennet B = 500 ml milk + 2ml of 0.234 % rennet + 2 % solution was pipetted out for each lot (500 ml) of milk. starter culture, C = 500 ml milk + 1ml of 0.139 % rennet + 2 % Methodology starter culture, D =500 ml milk + 1ml of 0.139 % rennet + 2 % starter Raw milk kept in refrigerator (at 4°C) for 2hours was then culture) of rennet were used. pasteurized at 68°C for 30 minutes and allowed to cool at 20°C. 2. The products made from different concentrations of The yoghurt made by Dairy Development corporation, was rennet were taken for sensory evaluation and the taken as starter culture. product having highest score was then taken for The basic steps for Quark making procedure was employed from optimization of sugar. For the optimization of sugar, + 4 the procedure provided by ptc 2007 (Netherland) . The details A1 = 2 %, A2 = 4 %, A3 = 5 % were used. Again these of the procedure are given below. 3 formulations were sensorily analysed 3. the best product was again taken for flavour Fresh milk (cow) optimization. The different flavors used were; vanilla, pineapple and orange and their concentrations were 125 ppm each. Pasteurized the milk at 68oC for 30min or 72oC for 15 sec. Sensory evaluation was carried out using numeric scoring

method described by American Dairy Science Association. Cool down to 20oc Analytical methods

The total solid content of the quark was determined by hot air Inoculate with 3% starters oven method according to AOAC5. Similarly, moisture content was determined by difference method according to AOAC5. The

fat content of the quark was determined by Gerber’s method for Add 1 ml of rennet solution fat determination. The protein content was determined by formal titration by following the method described by K.C. and

Rai6.The milk pH was determined directly with a digital pH Incubate 24 hrs at 20oC meter of CCT, Hattisar, Dharan. Acidity of the milk was determined according to Nepal Bureau of Standard7.The ash

content and lactose content of the quark was determined by Lane Cut the coagulum into large sized cubes and Enyon method8. Total coliform of the quark was determined by pour plate technique on Voilet Red Bile Agar (VRBA) medium. Total plate Drain the whey count (TPC) was determined by pour plate technique on plate count agar (PCA) medium. The total yeast and mould count was

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determined by pour plate technique on potato dextrose agar optimization of rennet. The different rennet concentration such (PDA) medium. as 1ml of 0.234 % rennet (A), 2ml of 0.234% rennet (B), 1ml of 0.139% rennet (C) and 2ml of 0.139% rennet (D) was used. Attribute Flavor Body Acidity Appearance Table 2 Mean sensory and chemical score of quark produced Formulatio texture b by different rennet formulations. 33 c a b A (3.46) 20.8 8.00 10.00 (1.41) (4.21) (0) a 28.4 b b a Values are the mean of three replicates and values in parentheses B 16.40 5.20 7.20 (2.28) (5.02) are S.D. values in the column having same superscript did not (4.39) (044) vary significantly (P > 0.01) with LSD. a 27.4 ab c a The flavor of product A prepared by using 1ml of 0.234 % C (3.71) 15.00 6.00 6.20 (1.30) (3.53) (0.70) rennet had significantly (P < 0.01) higher score than the others. The recommended rennet concentration for cheese given on the a 25.4 a d a label was 0.003 %. Among them 0.00234 % (1 ml of 0.234 %) D (2.88) 11.60 7.40 7.60 (1.81) (5.89) (0.89) gave the best results in terms of acidity, flavor and texture and it Statistical data analysis of The samples were analyzed by was selected for further improvement by manipulating the sugar Genstat programming (Genstat version 5) at 5 % level of content. significance. The mean values were compared using LSD and . This concentration was slightly lower as recommended for the best treatment was selected. cheese on the label. The product quark requires very low amount of rennet even though the concentration required is high because of different factors like storage temperature conditions, unsafe RESULTS AND DISCUSSION handling and transportation of rennet which could certainly decrease the rennet concentration. Quark was produced from cow milk having 4.3% of protein and 4% fat. The milk quality was in accordance with the actual Optimization of sugar concentration regulation of the milk and dairy products. The quak was made of Table 3 represents the sensory sugar formulation for good quality. The final product was analysed and the result is optimization of sugar content. The different sugar concentration

given in the table 1. This result was similar to the result obtained such as 2 % of sugar (A1), 4 % of sugar (A2) and 5 % sugar (A3) 1 by sohal et al. The microbiological quality of the product was was used for optimization of sugar level in quark. analysed and it was found the coliform count was nil, total plate count was 28 colonies at 10-3 dilution and yeast and mould Table 3. Analysis of difference in attributes of the count was 41 colonies for 10-3 dilution. This result is similar to formulations (sugar) 9 the Milanovicet al Attribute- Flavor Body Acidity Appearance

Formulati texture

Analysis of Final Product on↓ Table 1 Analysis of Product (refrigerated condition) a a a a A1 32.8 25 6 8 (1.73) Parameter values (4.88) (4.08) (1.63)

PH 3.4 b a a a A2 38.7 24.43 7.86 8.43 (0.98) Acidity 1.67% (2.93) (3.5) (1.07)

Protein content 4.20% a b a b A3 33.8 17.86 6.29 5.71 (1.60) Fat content 4% (4.56) (4.88) (2.69) Moisture 84.50%

TS 15.50% Values are the mean three replicates and values in the parentheses are S. D. values in the column having same

superscript did not vary significantly (p> 0.01). Optimization of rennet concentration for the preparation of

quark The flavor of product A2 prepared by using 4 % sugar Table 2. Represents the mean sensory score and chemical score concentration has significantly (p < 0.01) higher score than the of quark made by using different rennet concentration for the others. This result was similar to the result obtained by Atal,

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2006. She made soya yoghurt which was found to be the best in Figure. 1 Changes in pH and acidity of quark with time terms of taste when 4 % sugar was used. The total solid content under different storage conditions (broken lines are for after adding 4 % sugar was 17 % which was in the range (16-18) acidity) used by Miloavic, et al9 to prepare probiotic quark. In our Figure 1 shows that the pH of quark stored at room temperature context also the dairy industries of Nepal (Dairy Development (33°C±2) decreased significantly faster rate. The corresponding Corporation) use 4 % sugar for the preparation of yoghurt. So acidity of the lowest pH (3.2) is 0.45% (as lactic acid). The the product A2was selected for the further improvement by product in this stage was already in an unacceptable state with manipulating the color & flavor. respect to taste, smell, texture and appearance. This was natural Optimization of flavor because the activity of lactic acid bacteria and other spoilage bacteria was higher at room temperature compared to the lower Table 4 represents the mean sensory and chemical score of storage temperatures counterpart. There was no change in the quark made by using different formulation for the optimization pH and acidity in the control (deep freeze temperature, -18°C). of flavor the different formulation such as orange food color + For a storage period of a sample up to 17 days (samples were no flavor (A2a), no food color + pineapple flavor (A2b), no food not analyzed after 17 days), the acidity and pH showed a slight color + vanilla flavor. (A2c) change. Quark stored at refrigerated temperature (Temp. 4°C) Table 4: Mean sensory and chemical score of Quark produced behaved erratically for the first week and then stabilized at a pH by different flavor. of about 3.4 (corresponding acidity = 1.78) up to the 15th day of storage. The product was still acceptable up to the 15th day. This Attribute → Flavor Body Acidity Appearance implies that, quark can be typically stored at refrigerated Formulation↓ texture condition for about two weeks without much loss in sensory A a 29.67a 20.17a 6.17a 8.00a (2.68) quality. The shelf life obtained in this study was slightly lower 2 9 (4.76) (3.31) (0.98) than the result obtained by Miloavic, et al . The shelf life of probiotic quark made by Miloavic, et al9 was 30 days kept at ab a a a o A2b 35.83 23.33 6.67 11.83 lowerthan4 C (2.76) (2.065) (1.03) (2.13)

bc a b a A2c 37.50 22.33 8.00 11.17 Room Refrigerated (4.18) (3.50) (1.41) (2.13) Deep freeze

12 Values are the mean of three replicates and values in parentheses are S. D. values in the column having superscript did not vary 10 significantly (P> 0.01) with LSD. 8 The flavor of product A2a prepared by incorporating orange Smell score Smell food color (but without essence) did not significantly differ from 6 others at 5% level of significance. The data shows that there is a 4 considerable agreement between panelists. The panelists were familiar with the yogurt. The product A2c having vanilla flavour 2 was well percepted by the sensory panelist. So the product A2c was selected for the final product development. 0 0 5 10Days 15 20 Storage life of the product

Room Refrigerated Figure. 2 Changes in smell of quark with time under different 3.7 Days 3 storage conditions 3.6 The sample which is stored at room temperature (33ºC±2) had 3.5 2 slightly acceptable smell in the first day but in the second day it 3.4 was totally unacceptable ( score ≤ 5 has been arbitrarily ranked unacceptable in the present experiment). Refrigerated sample (~ 3.3 1 4ºC) was same as control (acceptable) up to six day. It indicates pH 3.2 that it has high quality life up to six day. 3.1 0

0 5 10 15 20 Acidity(% lactic acid) Days

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refrigerated temperature for 10 days without much loss in texture.

Room Refrigerated 12 Deep freeze

8 score 6

aste 4 T Appearancescore 2

0 Figure. 3. Changes in taste of quark with time under 0 5 10 15 20 different storage conditions Day s The quark sample which was stored at room temperature (33ºC±2) had slightly acceptable taste in the first day but in the Figure 5. Changes in appearance of quark with time under second day it was totally unacceptable. Refrigerated (4ºC) different storage conditions sample was same as control (acceptable) up to six days (Fig. 4), thereafter the quality decreased slightly and remained stable for The sample which was stored at room temperature (33ºC±2) had 15 days at a score of 7. It indicates that quark can be stored at slightly acceptable appearance in the first day but in the second refrigerated temperature for 15 days without much loss in taste. day it was totally unacceptable. Refrigerated (4ºC) sample was However, one also has to take into account the smell of the same as control (acceptable) up to six day. Thereafter the quality product (figure 3), in which case the overall acceptability will be decreased sharply and became no more acceptable. It indicates about 6 days. that quark cannot be stored at refrigerated temperature for more than a week without adversly affecting the appearance. Afterall,the refrigerated storage can hold quark for up to 6 days 14 Room in perfectly acceptable condition. Refrigerated CONCLUSION 12 Deep freeze Expon. (Room) Quark was made by using different formulations and they were 10 optimized for different parameters like rennet concentration, sugar concentration and flavor. Use of 1ml of 0.23% rennet was 8 found to be better than other concentration of rennet for flavor, -0.063x y = 11.452e texture and acidity. The 4 % of sugar concentration was found to R² = 0.9043 6 be the best in terms of taste, texture and acidity for the development of quark. The vanilla flavor was found to be the 4 best among the other flavors used. The shelf-life of the best product made was studied under room temperature (33±2oC),

Texture score Texture o o 2 y = 9.6349e-0.805x refrigerated condition (-4 C) and deep freezed condition (-18 C). R² = 0.9936 The product was acceptable up to 2 days kept in room 0 temperature whereas in refrigerated condition the high quality 0 5 10 15 20 life of the product was found to be 6 days and normal product Storage periods (days) life was found to be 15 days. In deep-freezed condition, the Figure 4 Changes texture of quark with time under different product remained unchanged up to 45 days. storage conditions ACKNOWLEDGEMENT The sample which was stored at room temperature (33ºC±2) had slightly acceptable texture in the first day but in the second day I would like to express my sincere thanks to the faculty of food it was totally unacceptable (Fig. 4). The quark sample stored technology, central campus of technology, Dharan and Sunsari under refrigeration (4ºC) was same in appearance up to six days, technical college Dharan for their support and encouragements thereafter the quality decreased slightly and remained stable for during the study. 10 days at a score of 6-7. It indicates that quark can be stored at REFERENCES

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1.Sohal, T.S., Studies To Improve the Shelf- Life and Consumer Acceptance of Quark. Master’s thesis, University Of Alberta, Canada; 1986 2. Garvie EI. Genus Leuconostoc. In: Sneath PH, Mair NS, eds, Bergey’s Manual of Systematic Bacteriology, 1984 2:1071- 1075. 3.Fankhauser,D. B. Fankhauser's Cheese Page.2007. Retrieved2007-09-23. http://biology.clc.uc.edu/fankhauser/Cheese/CHEESE.HTML 4. PTC + manual provided by Practical Training Centre Builds Bridges between theory and practices, Netherland 2007. 5. Howitz W, latimer GW, editors.Official Methods of Analysis of AOAC international, 18 ed. Md Publishing. Gaithersburg, 2005 6. K.C.Jagat and Rai, B.K. , Basic Food of Analysis Handbook. 1st Edition, Prompt Printers, 2007. 7. NDDB, . Laboratory Handbook for Dairy Industry.National Dairy Development Board. Nepal, 2001 8. Ranganna, S. (2000). Handbook of Analysis and Quality Control for Fruit and Vegetable Products, 2ndedition,TaTa McGraw-Hill Publishing Co. Ltd. 2000:pp 4-625. 9. Milanovic Spasenija D., Panic M. D. and Caric M. Đ. Quality of quark produced by probiotic application.Original scientific paper.APTEFF, 2004;35: 1-28.

Cite this article as: Yadav RS. Optimization of processing parameters and extension of shelf life of ‘quark’-a type of thick yoghurt. STCJ 2015,2(1): 38-43.